The present invention relates to building construction and more specifically to a composite steel and concrete framing system that forms a substantially monolithic support structure.
In the field of building construction, specifically the erection of multi-story buildings, the framing system constitutes the essential load-bearing structure that provides the stability and structural integrity of the building. The typical multi-story framing system consists of a plurality of stacked vertical columns interconnected with horizontal support beams. Typically, vertical columns and horizontal beams are composed of either steel, precast concrete, or formed-in-place concrete. Further, the horizontal beams typically support flooring sections of precast concrete, metal, or formed-in-place concrete. The framing system is designed to support well in excess of the anticipated loads developed by the structure itself and all live loads placed thereon. The forces generated by these loads are largely borne by the horizontal beams, the vertical columns and the connection members that join the beams and columns.
One known method of erecting a framing system is to pour concrete in place, utilizing suitable forms, to produce vertical columns, horizontal beams and floor sections. Pouring concrete in place has the advantage of producing buildings which are strong, highly rigid, durable and highly fire resistant. However, this method requires the use of labor intensive forms and complicated temporary supports which are expensive, easily destroyed and impede efficient work flow.
Another known method of erecting a framing system is to assemble precast concrete columns, beams and floor sections. This method has the advantage of rapid erection, with little need for temporary supports. However, precast concrete buildings tend to be less rigid than poured-in-place concrete buildings and have other inherent structural limitations. Still another often practiced method of erecting a framing system is to assemble steel columns and beams with steel or concrete floor sections. This method also has the advantage of rapid erection when steel precast concrete floor sections are used. Similar to the framing system assembled of precast concrete, steel buildings have inherent structural limitations. Most notably, these known framing systems are limited by the forces borne by the connecting membersxe2x80x94typically the weakest elements of the framing system.
Presently, no framing system provides a support structure which is both highly rigid and fire resistant as found with a poured-in-place system while easy to assemble as found with a steel system. Thus, there exists a need for a highly rigid and fire resistant framing structure which may be erected without temporary forms and complicated supports while overcoming the limitations found in connecting members.
The present invention addresses the shortcomings described above by providing a system of horizontal composite beams supported by vertical columns, which support flooring components such as precast planks or metal deck sections that receive poured concrete. A pourable bonding layer, such as a plasticized or cementitious material that hardens, tops the flooring components and bonds the flooring components, composite beams and columns. Each composite beam comprises a steel beam and interior of plasticized or solidifying material such as poured concrete. In the preferred embodiment, the steel beam includes a bottom plate, adjacent containment sides fortified by strap bars, studs, and horizontal support members. The horizontal support members provide a support surface for the floor components. Alternatively, the individual elements of the steel beam may be formed as a single, substantially monolithic unit. Reinforcing members such as rebar and post tensioned cables provide additional force bearing capacity to the composite beam.
In erecting the preferred framing system, concrete vertical columns are provided, each with at least one receiving saddle for supporting the end of a steel beam. The steel beams are raised and the flooring components, which span between adjacent steel beams, are set. Concrete is then poured to fill the interior of the steel beam; the strap bars act to resist the outward forces created by the wet concrete and the studs act to bond the cured concrete to the steel beam. Sufficient concrete is poured to fill the steel beam, flow into the hollow cores of precast floor planks, and rise to the upper surface of the planks. Alternatively, concrete is poured to fill the steel beam and added to fill a deck component to create a subfloor. Concrete can continue to be added to form a bonding layer and to fill all voids in or around the columns, thereby creating a substantially monolithic layer. Some blocking may be necessary at the columns to stop seepage of the concrete or bonding layer while the concrete is wet.
In a preferred embodiment, the composite beam is adapted for use along the perimeter of a horizontal level.